This tragic tale of a young boy bullied to death explores Susan Hill's perennial themes of persecution, punishment and the exploitation of the weak by the powerful. Joseph Hooper, a reticent widower, lives in a grand, isolated house with his young son, Edmund, and a collection of dead moths, inherited from his late father, a renowned lepidopterist.

One summer, their peace is disturbed by the arrival of widowed Helena Kingshaw and her 11-year-old son, Charles, who have answered an advertisement to housekeep for the Hoopers. The territorial, vindictive Edmund resents their presence and menacingly torments the sensitive Charles: "I DIDN'T WANT YOU TO COME HERE," he writes in a "welcome note". "We keep on not belonging," laments his traumatised victim. "There is no place for me." Yearning to escape, Charles pushes at the boundaries of his world, running away to a wood or climbing the eponymous castle, places that become powerful symbols of his profound alienation.

"We cannot fathom the minds of young children," thinks the delusional Mr Hooper. Susan Hill, however, delves beneath the surface of complex young minds, exposing not only their vulnerability and tenderness, their cruelty and malevolence, but also how parents end up turning a blind eye to their pain.